Fixation clamp

ABSTRACT

A fixation clamp for use in an external fixation system for holding bone fragments adjacent to each other with the help of fixation elements has at least one clamping assembly having a pair of jaws with at least two different size grooves to accommodate a bone fixation element such as a pin or rod. An alternate clamping assembly has at least three grooves wherein at least two of the grooves have a different size adapted to accommodate a correspondingly sized bone fixation element such as a bone pin. The longitudinal axes of the grooves define a polygon. The jaw pairs can be rotated about a central longitudinal axis to present different size reception cavities towards the pins or rocks depending on their diameter.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of European PatentApplication No. 09160445.4, filed May 15, 2009, entitled Fixation Clamp,the disclosure of which is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a fixation clamp and, moreparticularly, to a fixation clamp for use in an external fixation systemfor holding bone fragments adjacent to each other.

External fixation systems are widely used to connect two or more bonefragments to each other. Such systems comprise bone screws, pins, wireswhich are inserted directly into the bone material and these systems useexternal structural elements as fixation rods, bars and rings. In orderto connect the rods and bars to form a rigid frame, fixation clamps areused. Furthermore, fixation clamps are used to connect this screws andpins to the rigid frame to specifically hold bone fragments at anintended place.

One adjustable fixation clamp is known from U.S. Pat. Nos. 5,752,954 and6,080,153, the disclosures of which are incorporated herein byreference, comprising two pairs of jaws allowing clamping of a rod aswell as of a pin.

A clamp for multiple rod-shaped elements is known from U.S. Pat. No.7,618,417, the disclosure of which is incorporated herein by reference,having one single pair of jaws. However, such a clamp allows clampingmore than two, e.g. three or four rod-shaped elements such as pins withone single clamp, thus reducing the number of clamps. However, onefurther fixation clamp is necessary to fix the rod of said clamp to theframe of the fixation system.

U.S. Patent Publication No. 20060287652 discloses that the usualfixation clamps as e.g. known from U.S. Pat. No. 6,080,153 allowclamping of one single screw or pin to the frame and that this way toattach pins or rods leads to bulky fixation systems. Therefore U.S.Patent Publication No. 20060287652 discloses a fixation clamp addressingthis problem and comprises two pairs of jaws within which each pair ofjaws allows the introduction and clamping of two rods or pins etc. atthe same time.

These clamps according to the prior art either provide differentdiameters of the reception cavities, such as grooves, provided by thejaws to introduce different sizes of rods, pins or wires, or they relyon additional inserts as e.g. disclosed in U.S. Patent Publication No.20080065068. Such inserts reduce the diameter of the reception cavitiesto allow a secure fixing of differently sized rods, pins or wires.

BRIEF SUMMARY OF THE INVENTION

Solutions according to the prior art providing different diameterreception cavities necessitate provision of either a variety ofdifferent clamps or additional inserts.

It is one aspect of the invention to overcome this problem and toprovide the practitioner with a fixation clamp, especially for use in anexternal fixation system, which clamp can directly be used with avariety of differently sized rods, pins, screws and wires.

A fixation clamp for use in an external fixation system for holding bonefragments adjacent to each other with the help of fixation elementsincludes at least one clamping assembly, and a central locking shaftextending through the one or more clamping assemblies for blocking theposition of the clamping assemblies in a defined angular position;wherein each clamping assembly comprises two jaws, wherein each jawcomprises three grooves. The longitudinal axis of each groove isperpendicular to the locking shaft. One groove of one jaw corresponds toone groove of the other jaw to form a cavity to accommodate a bonefixation element. The longitudinal axes of the grooves may span atriangle, and wherein at least two grooves have a different size adaptedto accommodate a correspondingly sized fixation element. The fixationclamp groove may have a different size. The fixation clamp for use in anexternal fixation system for holding bone fragments adjacent to eachother with the help of fixation elements also may include at least oneclamping assembly having jaws mounted on a locking shaft, each jawhaving four grooves forming a cavity to accommodate a bone fixationelement along the longitudinal axis of the groove. The longitudinal axesof these grooves form a quadrilateral. At least two grooves have adifferent size adapted to accommodate a correspondingly sized fixationelement. Each groove of the fixation clamp has a different size whereintwo opposite grooves have the same size. The fixation clamp for use inan external fixation system for holding bone fragments adjacent to eachother with the help of fixation elements may have at least one clampingassembly including at least one pair of jaws mounted on a locking shafthaving five grooves to accommodate a bone fixation element along thelongitudinal axis of the grooves. The longitudinal axes of the groovesform a pentagon, and in that at least two grooves have a different sizeadapted to form a cavity to accommodate a correspondingly sized fixationelement. Each groove set forms a different size cavity. The grooves ofall clamping elements may be circular or triangular in crossection andmay comprise longitudinal ribs. Each clamping assembly preferablycomprises an anti-rotation pin extending from a first jaw into acomplementary recess in an opposite jaw. The grooves may be providedwithin outer side walls of each jaw in a way that the surface of afixation element pointing away from the locking shaft when inserted intoone groove is flush with the corresponding side wall.

A fixation clamp for use in an external fixation system for holding bonefragments adjacent to each other with the help of fixation elementsincludes a first and a second jaw member. A central locking shaftextends through the first and second jaw members wherein each jaw membercomprises at least three grooves. The longitudinal axis of each groovelies in a plane perpendicular to a longitudinal axis of the lockingshaft. One groove of the first jaw member corresponds to one groove ofthe second jaw member to form a cavity to accommodate a bone fixationelement. The longitudinal axes of the grooves are all non-parallel inthe plane. The first and second jaw members have a face parallel to theplane containing the longitudinal axis of the at least three grooves. Ananti-rotation pin extends perpendicular to the plane of the face of thefirst jaw extends into a bore in the planar face of the second jawmember. The pin and bore are located within a geometric shape formed bythe grooves. The fixation clamp for use in an external fixation systemfor holding bone fragments adjacent to each other with the help offixation elements may have first and second jaw members having fourgrooves to accommodate a fixation element along the longitudinal axis ofthe groove wherein the longitudinal axes of said grooves form aquadrilateral. At least two grooves have a different size adapted toaccommodate a correspondingly sized fixation element.

The fixation clamp for use in an external fixation system for holdingbone fragments adjacent to each other with the help of fixation elementsmay include first and second jaw members having five grooves toaccommodate a fixation element along the longitudinal axis of thegrooves. The longitudinal axes of the grooves form a pentagon, and inthat at least two grooves have a different size adapted to form a cavityto accommodate a correspondingly sized fixation element.

The clamp according to the invention allows readily treating differenttypes of fractures or connecting bones of different sizes to each other,since usually different pin diameters are required. The clamp provides aplurality of different couplings possibilities which is an advantage,avoiding mismatching of components, which can lead to insufficientconnecting strength. The clamp according to the invention also allowsfor clicking in rods from the side. The clamp can be built based on theusual metallic components and can comprise non-magnetic and nonconductive materials, which are safe for temporary exposition in a MRIscanner, and can furthermore comprise plastic or composite materials orhave electrical insulating cover surfaces.

It is an advantage of the clamp according to the invention that afterhaving clamped a bone screw with one clamping assembly, a practitionerattaching subsequently a rod of an external fixator to the otherclamping assembly can check the robustness of the external fixator, andif the practitioner finds that the rod used is not stiff enough, onesimply opens the other clamping assembly, removes the thinner rod, turnsthe other clamping assembly e.g. 60 degrees into one direction or theother around the longitudinal axis to align a larger reception cavitywith the new thicker rod and replaces said rod. This change does notnecessitate the replacement of the clamp itself and is thus faster andmore reliable since the clamping of the bone screw is not changed, andthe use of a second sterile clamp at said time is avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described in the followingdescription with reference to the drawings, which are provided for thepurpose of illustrating the present preferred embodiments of theinvention and not for the purpose of limiting the same. In the drawings,

FIG. 1 is an exploded view of a first embodiment of the clamp of thepresent invention;

FIG. 2 is a top view of the clamp according to FIG. 1;

FIG. 3 is a first side view of the assembled clamp of FIG. 1;

FIG. 4 is a second side view of the assembled clamp of FIG. 1 from adifferent direction than FIG. 3;

FIG. 5 is a top view of an inner jaw portion of the clamp according toFIG. 1;

FIG. 6 is a top view of an outer jaw portion of the clamp according toFIG. 1;

FIG. 7 is a cross-section of the clamp shown in FIG. 4;

FIG. 8 is an exploded view of a second embodiment of the clamp of thepresent invention;

FIG. 9 is a top view of the clamp shown in FIG. 8;

FIG. 10 is a cross-section of the clamp of FIG. 8 along line X-X of FIG.9;

FIG. 11 is a top view of the clamp of the present invention with twoattached fixation elements;

FIG. 12 is a front view of the clamp with two attached fixation elementsaccording to FIG. 11; and

FIG. 13 is a right side view of the clamp of FIG. 11 with two attachedfixation elements.

DETAILED DESCRIPTION

Referring to FIG. 1 there is shown a perspective exploded view of apreferred first embodiment of a clamp 10 pursuant to the invention. Theclamp 10 consists of a first clamping assembly 20 and a second clampingassembly 30 and a shaft 40 which is positioned through bores 21, 31within the two clamp assemblies 20, 30 along the longitudinal axis ofshaft 40. Each clamping assembly has a first jaw 11 and a second jaw 12.Shaft 40 is preferably a locking element adapted to allow the closingthe clamp assemblies 20 and 30. Shaft 40 enters a first jaw 11 through awasher 41. Washer 41 may have a part-spherical shape for receipt on apart-spherical surface of bore 21. The shaft 40 comprises a proximalportion 42 and a reduced diameter portion 43 which is followed by athreaded portion 49. The outer threaded portion 49 is adapted to bescrewed into a complementary inner thread which may be formed within thedistal most jaw 11 (bottom jaw of FIG. 1) so that turning the head ofthe shaft 40 changes the longitudinal position of the shaft 40 againstthe bottom jaw 11. This allows for opening or closing the entire clamp10 against the force of a spring 15 provided between the two clampassemblies 20 and 30. Obviously a separate nut could be provided ratherthan threading the bore in lowermost jaw 11 of FIG. 1. Spring 15 ispreferably positioned in corresponding reception cavities in jaws 12.Instead of a spring 15, provided around shaft 40, it is possible toprovide a different spring means as Belleville washers or an elasticcompressible solid or foam. Upon closing of the clamp assemblies 20 and30 the jaws 12 adjacent spring 15 can eventually come into contact andthen the anti-rotation surface 44 which is provided in both surfaces ofthe jaws, fixes the angular orientation of each clamping assembly 20 and30 against each other.

Preferably after having mounted the shaft 40 with the thread 49 withinthe bottom jaw 11, the end portion of the thread 49 is deformed ordestroyed through pressure to ensure that the shaft 40 cannot be removedfrom the clamping assemblies 20, 30 to maintain the clamp as one singlepiece.

As discussed above, each clamping assembly 20 or 30 comprises twoopposing clamping jaws 11 and 12. These jaws 11 and 12 are essentiallysimilarly shaped on the sides facing each other except for a pin 13which extends into a corresponding bore 14 in clamping jaw 12. Thispin-bore connection which is oriented along or parallel to thelongitudinal axis of the clamping device is an anti-rotation device forjaws 11 and 12. Once engaged jaws 11, 12 cannot change their mutualangular orientation. The plane surface of jaw 11 facing the planesurface of jaw 12 is provided with three spacers 17 arranged in thecorners of the surface. The spacers 17 have a mostly triangular form anda height to allow the function of a counter bearing as explained below.Additionally, the spacers 17 result in the two plane surfaces of jaws 11and 12 being spaced so that the open areas between these surfaces can becleaned.

The jaws 11 and 12 are provided with three grooves 51, 52 and 53.Grooves 51, 52 and 53 are all provided in a same plane perpendicular tothe longitudinal axis of shaft 40. In that plane they are orientedperpendicular to the radial direction from the center of the bore 21 or31. As such the grooves 51, 52 and 53 are parallel to outer side wall61, 62 or 63 of each pair of triangularly shaped jaws 11 and 12.

Each pair of grooves 51, 52 or 53, respectively, in each jaw 11 and 12,define one reception cavity, i.e. a first reception cavity 71, a secondreception cavity 72 and a third reception cavity 73. The grooves 51, 52and 53 are each formed as a rounded semi-spherical recess in section toprovide reception cavities 71, 72 and 73 which accommodate cylindricalpins or rods 100 with a defined diameter (see FIGS. 11 to 13), if theclamp is closed. The outer side walls 61, 62 or 63 can comprise aninclined sliding surface to allow for easy clipping or snapping in ofsuch pins or rods 100 into the corresponding cavities. The grooves 51,52, 53 are formed as rounded semi-spherical recesses in a section. Thismeans that the recesses provided by the grooves 51, 52, 53 have a hollowcylindrical shape to accommodate rod-shaped elements.

All three grooves 51, 52 and 53 have different sizes so that thecorresponding reception cavities 71, 72 and 73 have three differentsizes. In other words each reception cavities 71, 72 or 73 is adapted toaccept a different fixation element, i.e. a rod, screw, pin or wirehaving a different diameter. One preferred embodiment of the firstclamping assembly 20 has grooves to accept fixation elements having adiameter of 12 mm, 8 mm and 5 mm, respectively. A different embodimentmay have a sequence of diameters of 8 mm, 6 mm and 4 mm, respectively.

The second clamping assembly 30 according to the embodiment of FIG. 1also comprises two jaw portions 11 and 12 and these comprise threegrooves 51, 52, 53. These grooves 51, 52, 53 also comprise a sequence ofdifferent sizes. In the embodiment shown the inner jaws portion 12 havean identical structure as have the outer jaws 11, especially in view ofthe anti-rotation device 44, the second bore for a spring 15 as well asribs 45 inside the grooves 51, 52, and 53.

Within a preferred embodiment the first clamping assembly 20 maycomprise a sequence of smaller size cavities, e.g. 7 mm, 5 mm and 3 mm;or 6 mm, 5 mm and 4 mm; and the second clamping assembly 30 may comprisea sequence of larger sizes, e.g. 13.5 mm, 12 mm and 10 mm. Differentsizes are possible, usually for wires starting from 2 mm diameter up tothicker rods with a diameter of 30 mm are used within such a clamp 10.Such a clamp 10 allows the use of one single versatile clamp, whereinthe first clamping assembly 20 is used to fix a specific pin or screw orwire having a diameter for which one of the reception cavities 71, 72 or73 is adapted. The user takes the clamp 10 and orients or rotates thefirst clamping assembly 20 into the correct alignment so that the pin orscrew can be clipped into the corresponding reception cavity.

Then the clamp 10 can be clamped on a rod of an external fixator withthe help of the second clamping assembly 30. The second clampingassembly 30 can be oriented in a way so that the rod can be clipped intothe corresponding reception cavity. It is an advantage of the clamp 10having two clamping assemblies 20 and 30 according to the invention,that a practitioner attaching such a clamp at a bone screw with oneclamping assembly 20 and subsequently a rod of an external fixator tothe other clamping assembly 30 can check the robustness of his externalfixator, and if it is found that the rod used is not stiff enough, onesimply opens the second clamping assembly 30, removes the thinner rod,turns the second clamping assembly 30 e.g. 60 degrees in one directionor the other around the longitudinal axis, to align the larger receptioncavity with the new thicker rod and replaces it. This change does notnecessitate the replacement of the clamp 10 itself as necessary withprior art systems. The method to replace such a rod 100 is faster andmore reliable since the clamping of the bone screw is not changed, andat the same time avoids use of a second sterile clamp.

It is of course also possible that the second clamping assembly 30 is atraditional clamping assembly or even any other element known in theprior art with clamping elements. The object of a versatile clampingassembly is already achieved through one first clamping assembly 20,since it allows clamping one of three different sizes of screws, pins ofwires through simple reorientation of the first clamping assembly 20.

FIG. 2 shows a top view of the clamp according to FIG. 1. Since theembodiment of FIG. 1 comprises three grooves 51, 52 and 53, there arethree side walls 61, 62 and 63, which provide, when looked from above asin FIG. 2 a triangular shape of each clamping assembly 20 or 30.

FIG. 3 shows a first side view of the clamp of FIG. 1 and FIG. 4 shows asecond different side view of the clamp 10 of FIG. 1 from a differentdirection. Identical reference signs are used for identical featureswithin the same embodiment and are used for identical or similarfeatures in further embodiments.

It is clear from FIG. 3 that the first reception cavity 71 is identicalin size and allows for insertion of a large rod. From FIG. 4 it can beseen that the third reception cavity 73 are small cavities, e.g. for apin. In this embodiment, second cavities 72 have an intermediate size.From FIG. 4 it can be seen that the depicted embodiment has a decreasingsize sequence of reception cavities 71, 72 and 73 in the upper firstclamping assembly 20 in clockwise direction whereas the depictedembodiment has a decreasing size sequence of the reception cavities 71,72 and 73 in the lower second clamping assembly 30 in counter-clockwisedirection.

Referring to FIG. 5 there is shown a top view of an inner jaw portion12, whereas FIG. 6 shows a similar view on a corresponding outer jawportion 11. It is clear that each jaw portion 11 or 12 of any clampingassembly 20, 30 according to the invention comprises three differentlysized grooves 51, 52 and 53, respectively. The longitudinal axes ofthese grooves 51, 52 and 53 are oriented in an angle of 60 degree one toanother. However, these angles of 60 degree are not mandatory. It isonly necessary that the total internal angle of the triangle provided bythese three grooves 51, 52 and 53 is 180 degrees. The grooves are alsoin the same median plane which indicates that only one pin, screw or rodcan usually be introduced in one of the grooves 51, 52 or 53 and such anintroduction blocks the other empty grooves. It is an aim of thisorientation to provide a simpler mounting of a fixation device, sincebased on the chosen pin or screw a clamp of the invention can be chosenand through rotation of the clamping assembly the correct sizedreception cavities 71, 72 or 73 is usable for a well clamped connection,wherein the clipping of the pin or screw from the open side furtherfacilitates their introduction.

It is clear from FIGS. 5 and 6 that the grooves 51, 52 and 53 mutuallyintersect. The inner jaw portion 12 shown in FIG. 5 comprises ribs 45which are oriented in the longitudinal direction of the grooves 51, 52and 53. Each groove is provided with two lines of ribs 45, which arearranged one behind the other and thus can also be described to be asingle line interrupted in the middle part. Of course there may be oneor no ribs 45, or there may be more than two lines, and these lines canbe provided uninterrupted, although the embodiment with interrupted ribs45 as well as two lines of these ribs 45 is preferred.

It is possible to deviate from the correct triangular orientation of thegrooves; especially the angle between the largest groove 51 and theneighboring grooves can be less than 60 degree, so that the anglebetween the longitudinal axes of the grooves 52 and 53 is greater then60 degrees.

It is also possible, in different embodiments, not shown in the figures,to provide four, five or more grooves. If four grooves are provided,then the form of such a clamping assembly 20 seen from above is a squareand each jaw comprises four grooves joining in the corners in atpreferably a right angle. Then a sequence of four sizes of the receptioncavities is possible as 12 mm, 8 mm, 6 mm and 4 mm. If five grooves areprovided, then the form of such a clamping assembly 20 seen from aboveis a pentagon and each jaw comprises five grooves joining in thecorners, preferably at an angle of around 108 degrees. Then a sequenceof five sizes of the reception cavities is possible as 12 mm, 20 mm, 8mm, 6 mm and 4 mm. Of course deviations from such a symmetrical polygonare possible.

It is noted that the spacers 17 and thus the counter bearings as well asthe corners of the jaw planes are not symmetrically positioned in viewof the central bore 21 of a jaw. The deviation from the symmetric formis smaller for the largest reception cavity 71 and larger for thesmallest reception cavity 73. However, this is not problematic, sincethe largest reception cavity 71 with the smallest deviation accepts thelargest rod and thus the largest forces, wherein the largest deviationoccurs for the smallest reception cavity and the function of such asmall reception cavity resides in accepting a limited force.

FIG. 7 shows a cross-section of the clamp according to FIG. 4, whereinthe clamp 10 is shown in a premounted state, i.e. the spring 15 is undertension. The upper jaw 11 of the first clamping assembly 20 is thereforepushing the rounded counter piece 41 against a flange 40 a of the headof shaft 40. The jaw 11 has around its bore 21 a rounded part-sphericalrecess to accommodate the washer 41. This enables a pivoting movement ofthe upper jaw 11 against the axis of the shaft 40, since the shaft 40comprises a reduced diameter portion 43 extending over the whole lengthof the jaws 11 and in both assemblies. It is also possible that there isno play between shaft 40 and jaw 11; the bore 21 just allows theintroduction of the shaft 40. Then jaw 11 and jaw 12 can only effect atranslatory movement.

The pin 13 of the upper jaw 11 is lodged in a recess 16 in the bore 14.It is possible but not necessary that the pin 13 or the recess 16receives an elastic fitting piece allowing elastic movements of the pinwithin the recess 16.

The shaft 40 as part of a locking element is threaded into the lower jaw11 of the second clamping assembly 30 and is further connected with acounter nut 46, which is fixedly lodged on shaft 40. Therefore the twoclamp assemblies 20, 30 can be opened and closed through turning thehead of shaft 40 and thus turning shaft 40 with the blocking counter nut46 and in the jaw thread. The counter nut 46 can then be used to lockshaft 40 from further rotation

The combination of shaft 40 and counter nut 46 can also be replaced by asingle screw to be screwed into the lower jaw 11 of the second clampingassembly 30. Threading may be provided in the bore or the screw mayexhibit self-tapping threading. Quite generally, a locking element maybe provided which may be a lever locking element or a bayonet lock.Among these locking elements may also be supporting disks or tootheddisks, which, for the sake of simplicity, are not shown in the drawings.

FIG. 8 shows an exploded view of a second embodiment of a clamp 10 a ofthe present invention; FIG. 9 shows a top view of the clamp and FIG. 10shows a cross-section of the clamp along line X-X in FIG. 9. Thesequence of sizes for the first clamping assembly 20 a is 13.5 mm, 8 mmand 5 mm. The choice of this sequence depends on the intendedapplication (e.g. which limb is to be treated) of the external fixatorset and follows the needs of the application.

The clamping assemblies 20 a, 30 a of the embodiment have a triangularform, as can be seen from FIG. 9, having defined straight side walls 61,62 and 63 and identically curved transitory portions. For a descriptionof features which are identical to the clamp of FIG. 1 reference is madeto that description.

Instead of spacers 17 in the corners of the plane surface of the jaws 11a there are provided two flattened semi-spherical spacers 27 on thesurface. As mentioned above, the first clamping assembly 20 a comprisesa sequence of larger sized reception cavities 71, 72, 73. The lowersecond clamping assembly 30 comprises a different sequence of smallersized reception cavities 71, 72, 73. The corresponding grooves 51, 52and 53 within the lower jaw 11 a are not semi-spherical as with theclamp of FIG. 1 but are triangular or v-shaped grooves 51, 52, 53 havinga bottom line 54 of a v-shaped groove. The corresponding groove portionin the opposite jaw 12 a is a rounded groove, in FIG. 10 receiving thenumeral 55, so that slightly different sizes of elements can be clamped.However, the sizes of the grooves 51, 52 and 53 are neverthelessdifferent one from the other.

Usually the rounded grooves are intended to be used especially withcarbon rods and allow high precision clamping under all circumstances,whereas the triangular grooves are more flexible. They usually providetwo sizes with one groove, e.g. 4-5 mm, 5-6 mm and 7-8 mm for threegrooves.

Element 47 is a steel helicoil inserted into an aluminum jaw 11 a toprovide a better counter thread for the thread 49 of shaft 40. The endportion 49 of shaft 40 is hollow with an additional inner thread toaccommodate the outer thread 58 of a counter nut 48.

FIG. 11 shows a top view of the clamp 10 a of the present invention withtwo attached fixation elements 100 and 101. FIG. 12 shows a front viewof the clamp according to FIG. 11; and FIG. 13 shows a view from theright.

The fixation elements shown here are small-sized rods. Fixation element100 is introduced in the smallest size reception cavity 73 of the firstclamping assembly 20 leaving the middle-sized reception cavity 72 andthe large-size reception cavity 71 empty. From FIG. 12 it can be seenthat the introduction of rod 100 blocks the section of reception cavity72. From FIG. 13 it can be seen that the introduction of rod 100 alsoblocks the section of reception cavity 73. Therefore a clamping assembly20 is usable for one single rod or pin at the same time, here rod 100.

The same is true for rod 101 used in connection with the second clampingassembly 30 a. In this embodiment, the two clamping assemblies have anidentical sequence of reception cavity sizes, i.e. there are three sizesof reception cavities twice in the clamp 10 a. As mentioned above it ispossible to provide different reception cavity sizes in the two clampingassemblies 20, 20 a and 30, 30 a. Therefore it is possible to have up tosix different sizes of reception cavities within one clamp consisting oftwo clamping assemblies according to the invention, e.g. 3 mm, 4 mm, 5mm, 6 mm, 8 mm, and 10 mm. It has to be noted that the sequence is notnecessarily distributed according to size. One clamping assembly canhave sizes 3 mm, 5 mm and 8 mm, whereas the complementary assembly hasthe sizes 4 mm, 6 mm and 10 mm, showing a mixed sequence.

It is also possible to use two rods 100 and 101 with one single clampingassembly 20, 20 a, if the rods are shorter so that the rods 100, 101cannot intersect behind the clamp 10. This allows providing a so-calledY-frame with one single clamping assembly, wherein the two rods or bonescrews are oriented within an angle of 60 degrees.

It is noted that the grooves 51, 52 and 53 are preferably provided at adistance from the center of the clamp 10 so that the rods, pins orscrews which are to be inserted in the created reception cavities areflush with the side walls 61, 62 or 63 as it can be seen in FIG. 11.

The single clamping assemblies 20, 20 a or 30, 30 a can be combined indifferent ways. If a clamping assembly having round grooves is called arod clamping assembly and a clamping assembly having triangular groovesis called a pin clamping assembly then several clamps having two singleclamping assemblies 20, 20 a or 30. 30 a are possible, i.e. pin-pin,rod-pin or rod-rod.

The clamp or articulation element according to the invention has atleast two opposing first and second clamping jaws 11, 11 a and 12, 12 a,providing one lateral open free space for laterally receiving arod-shaped element 100. The lateral open free space is formed throughgrooves and is in the form of an open slot. It is also possible toaccommodate inserts, i.e. a jacket element adapted to be inserted in onejaw of the clamp to modify the space available for the rod-shapedelement. Such an insert can be built according to e.g. U.S. PatentPublication No. 20080065068 and introduced into the reception cavitiesto have additional versatility. On the other side it is also possiblethat a triangular clamp 10, 10 a according to the invention comprises aclamping assembly 20, 20 a or 30, 30 a having two identical grooveswithin the three grooves. This is especially true, if according to adifferent embodiment, four, five or more grooves are provided.

For four grooves it is possible to combine the advantage of using twosizes of reception cavities which are provided one opposite to theother. Then—in clockwise direction—the four cavities may be: small,large, small, large; which allows the parallel introduction and fixationof two small pins or two large rods, since the square disposition do nothinder the simultaneous introduction of two pins or rods. The same istrue, if five grooves/reception cavities are provided, since an angle ofaround 108 degrees, two out of the five reception cavities can be used.

Within a preferred embodiment it is contemplated that at least the lowerjaw 11, 11 a of the second assembly 30, 30 a has a different color thenthe other jaws to indicate that there is a specific sequence of sizes.It is e.g. possible that said lower jaw is green, indicating that saidclamping assembly 30, 30 a provides a sequence of larger receptioncavities (13.5 mm, 10 mm, 8 mm) whereas the other clamping assembly 20,20 a provide smaller reception cavities (e.g. 6 mm, 5 mm and 4 mm). Itis also possible to provide the upper most jaw 11, 11 a of the firstclamping assembly 20, 20 a with a different color, e.g. blue to indicatethat said clamping assembly 20 provides the smaller reception cavities.Then of course, blue-blue, blue-green and green-green combinations ofclamps 10, 10 a would provide a high usability of use with directindication for the user, which clamp he should choose. This color modelcan be extended to a third of fourth color according to the abovementioned sequences of reception cavity sizes.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

The invention claimed is:
 1. A fixation clamp for use in an external fixation system for holding bone fragments adjacent to each other with the help of fixation elements, comprising at least one clamping assembly, and a central locking shaft extending through the at least one clamping assembly for blocking the position of the at least one clamping assembly in a defined angular position; wherein the at least one clamping assembly comprises first and second jaws, the first and second jaws define outer side surfaces wherein each first and second jaw comprises three and only three grooves, wherein the longitudinal axis of each groove lies in a plane that is perpendicular to the locking shaft, wherein one groove of one jaw corresponds to one groove of the other jaw to form a recess to accommodate a bone fixation element, wherein the longitudinal axes of the grooves on the first and second jaw span a triangle, and wherein at least two grooves in the first and second jaws have a different size adapted to accommodate a correspondingly sized fixation element wherein the longitudinal axis of each groove in the first and second jaws intersects the longitudinal axis of each of the other two grooves forming three angles totaling 180°, wherein two of the three grooves of each jaw member intersect within the outer side surfaces of each jaw.
 2. The fixation clamp according to claim 1, wherein each groove in the first and second jaw has a different size.
 3. The fixation clamp according to claim 1, wherein the grooves either in the first and second jaws are circular or triangular in cross section.
 4. The fixation clamp according to claim 1, wherein the grooves in the first and second jaws comprise longitudinal ribs.
 5. The fixation clamp according to claim 1, wherein the at least one clamping assembly comprises an anti-rotation pin extending from the first jaw into a complementary recess in the second jaw.
 6. The fixation clamp according to claim 1, wherein the grooves in the first and second jaws are provided within the outer side surfaces of the corresponding jaw and spaced from the central locking shaft so that the surface of a fixation element pointing away from the locking shaft when inserted into one groove is flush with the corresponding outer side surface.
 7. A fixation clamp for use in an external fixation system for holding bone fragments adjacent to each other with the help of fixation elements, comprising at least one clamping assembly having first and second jaws mounted on a locking shaft, each jaw defining an outer surface and having three and only three grooves to accommodate a bone fixation element along the longitudinal axis of each groove in the first or second jaws, wherein the longitudinal axes of said grooves form a triangle, and in that at least two grooves have a different size adapted to accommodate a correspondingly sized fixation element wherein the triangle has three angles with each angle being 60°, wherein two of the three grooves in each of the first and second jaws intersect within the outer surface of each jaw.
 8. The fixation clamp according to claim 7, wherein each of the three grooves in the first and second jaws has a different size.
 9. The fixation clamp according to claim 7, wherein the grooves in the first or second jaws are either circular or triangular in cross section.
 10. The fixation clamp according to claim 7, wherein the grooves in the first and second jaws comprise longitudinal ribs.
 11. The fixation clamp according to claim 7, wherein the at least one clamping assembly comprises an anti-rotation pin extending from the first jaw into a complementary recess in the second jaw.
 12. The fixation clamp according to claim 7, wherein the grooves in the first and second jaw are provided within outer side walls of the corresponding jaw in a way that the surface of a fixation element pointing away from the locking shaft when inserted into one groove is flush with the corresponding side wall.
 13. The fixation clamp according to claim 7, wherein two facing grooves on the first and second jaws have the same size.
 14. The fixation clamp as set forth in claim 7 wherein the three angles are each 60°.
 15. A fixation clamp for use in an external fixation system for holding bone fragments adjacent to each other with the help of fixation elements, comprising at least one clamping assembly including first and second jaws mounted on a locking shaft, the first and second jaws having outer side surfaces and three and only three grooves to accommodate a bone fixation element along the longitudinal axis of the grooves, wherein the longitudinal axes of said grooves form a triangle, and in that at least two grooves of the first and second jaws have a different size adapted to accommodate a correspondingly sized fixation element, the three grooves on the first and second jaws each lying in a plane perpendicular to a longitudinal axis of the locking shaft and are oriented at 60° angles to one another, wherein two of the three grooves of each jaw member intersect within the outer side surfaces of each jaw.
 16. The fixation clamp according to claim 15, wherein each groove on the first and second jaws has a different size.
 17. The fixation clamp according to claim 15, wherein the grooves in the first and second jaws are either circular or triangular in cross section.
 18. The fixation clamp according to claim 15, wherein the grooves in the first and second jaws comprise longitudinal ribs.
 19. The fixation clamp according to claim 15, wherein the at least one clamping assembly comprises an anti-rotation pin extending from a first jaw into a complementary recess in the second jaw.
 20. The fixation clamp according to claim 15, wherein the grooves in the first and second jaws are provided within the outer side surfaces of the corresponding jaw and spaced from the locking shaft that the surface of a fixation element pointing away from the locking shaft when inserted into one groove is flush with the corresponding outer side surface.
 21. A fixation clamp for use in an external fixation system for holding bone fragments adjacent to each other with the help of fixation elements, comprising: a first and a second jaw member, each jaw member having a surface facing the other jaw; a central locking shaft extending through the first and second jaw members along a longitudinal axis; wherein the facing surfaces each jaw member comprises three and only three grooves, wherein the longitudinal axis of each groove in the first and second jaw members lies in a plane perpendicular to the longitudinal axis of the locking shaft, wherein one groove of the first jaw member corresponds to one groove of the second jaw member to form a cavity to accommodate a bone fixation element, wherein the longitudinal axes of the three grooves on the first and second jaw members form a triangle in the plane, wherein the first and second jaw members have a face parallel to the plane containing the longitudinal axes of the three grooves, an anti-rotation pin extending perpendicular to the plane of the face of the first jaw extends into a bore in the planar face of the second jaw member, the pin and bore located within the triangle formed by the grooves, the longitudinal axes of the three grooves forming three angles totaling 180°, wherein a portion of the facing surface of one jaw located between the three grooves and the central locking shaft at an intersection of two of the grooves stands outwardly of a remaining portion of the facing surfaces to space the facing surfaces apart.
 22. The fixation clamp as set forth in claim 21 wherein the three angles are each 60°. 